Deactivation of Copper Catalysts During CO2 Reduction Occurs via Dissolution and Selective Redeposition Mechanism

As electrochemical CO2 reduction (ECR) approaches industrialisation levels, addressing the challenge of uncontrolled restructuring and deactivation of copper (Cu) catalysts during operation is essential for the regulation of this phenomenon. Two different catalysts were prepared, each showing distinct changes in ECR products selectivity over prolonged operation. The detection of dissolved Cu species during electrolysis confirms the intermediates mediated Cu0(s) dissolution mechanism at ECR potential, namely -0.8 to -1.1 V vs. reversible hydrogen electrode. A dynamic equilibrium between dissolution and subsequent redeposition leads to morphological restructuring. Additionally, our findings suggest that the electrodeposition of dissolved Cu species is biased towards less active sites due to their lower coverage by reaction intermediates such as adsorbed CO. The iterative cycles of the dissolution-redeposition mechanism at ECR potential lead to the growth of the less-active Cu surface at the cost of the more-active one. This gradual yet persistent restructuring mechanism consequently shifts selectivity away from ECR and towards hydrogen production. Both catalysts exhibited this general behaviour, although at different rates.